Manila will bring up Beijing's continued aggression in the South China Sea when Southeast Asian leaders meet in Thailand later this week, Philippine officials said Tuesday, a week after a Chinese ship rammed a Filipino fishing boat in the disputed maritime region.

Leaders from the Philippines and nine other members of the Association of Southeast Asian Nations are to gather in Bangkok for an ASEAN summit to tackle regional issues. These will include economic integration and terrorism, as well as ongoing wrangling over the potentially mineral-rich South China Sea.

"[The] South China Sea will be on the agenda and the leaders are going to exchange views on this issue," Junever Mahilum-West, assistant secretary at the Philippine foreign affairs department, told reporters on Tuesday. She emphasized that the regional bloc was negotiating a "code of conduct" for the sea region.

While China and the ASEAN bloc had agreed to solve overlapping territorial claims to the sea peacefully and put in place a regional mechanism to avert conflict, Beijing has not ceased its expansion in the waterway.

Last week, the Philippines filed a diplomatic protest against China after Manila said that a Chinese ship sank a fishing boat in an area within the Philippines' exclusive economic zone, leaving 22 Filipino fishermen floating at sea until they were rescued by a Vietnamese boat. Officials said a Chinese militia ship likely was behind the ramming.

President Rodrigo Duterte, a close ally of Chinese leader Xi Jinping and known for publicly cursing foreign governments that displease him, has come under pressure to toughen his stance against Beijing instead of dismissing the case outright.

Duterte may bring up the June 9 incident at Reed Bank when he meets with his peers in Bangkok later this week, Mahilum-West said.

"There is an opening to raise these issues. Because incidents like what happened emphasized the importance of having a code of conduct, so that we could avoid, we could prevent these incidents from happening in the future," she said.

The Chinese embassy in Manila on June 15 confirmed that a Chinese trawler, Yuemaobinyu 42212, "bumped into" the Filipino fishing boat, but denied that it was a "hit and run" incident, as claimed by Philippine officials.

"The Chinese captain tried to rescue the Filipino fisherman, but was afraid of being besieged by other Filipino fishing boats," the embassy said in a statement.

But the Filipino captain and some of his crewmen in televised interviews told a different story, saying they had spent hours in the water awaiting help before they were picked up by a Vietnamese vessel.

A legally binding code of conduct will help govern actions by Beijing and other claimants in the South China Sea. China claims most of the mineral-rich sea region, including areas that reach the shores of its smaller neighbors. Brunei, Malaysia, the Philippines, Vietnam and Taiwan also have overlapping claims in the sea.

"It's precisely why we need a code, so that this incident could be taken on board and we would have a guideline for countries in the region on how to behave, on how to act in order to prevent these incidents that caused some ... that might cause tension in the region," Mahilum-West said.

Ordinary maritime incident

After days of keeping mum on the issue, Duterte broke his silence Monday, calling the incident "an ordinary maritime traffic accident" and asked the Navy and troops to "stay out of trouble. "

"What happened [is] there is a collision. That is a maritime incident. Don't believe stupid politicians. They want the Navy to go there. You do not send grey ships there. It's just a collision, do not make it worse," Duterte said.

The president said people should wait and listen to China's side, saying an investigation had begun and Beijing "had the right to be heard."

He also warned the Navy from meddling, noting that a wrong move in the region, such as sending warships into the area, could fuel tensions.

"You know how it is with soldiers, a miscommunication could lead to death," he said.

But Duterte's critics, including opposition Sen. Panfilo Lacson, a retired police general, slammed Duterte's perceived inaction, as he underscored that the Philippines was a defense treaty ally of the United States and could count on its military support in times of aggression.

Duterte left Filipinos "heartbroken," he said.

"He forgot to explore all resources available before exercising his last option of surrender. The MDT (mutual defense treaty) is one yet-untapped weapon. I am not suggesting World War III, but at least it can make China feel the balance of power in the WPS," Lacson said, apparently referring to the West Philippine Sea, the other name of the South China Sea.

Chinese mock flags burned

Duterte's soft stance against China has been challenged by nationalist groups repeatedly. On Tuesday, one group marched in Manila streets and burned 22 Chinese mock flags as they condemned the treatment of the Filipino fishermen.

The rally, dubbed as Justice for Philippines, was organized by a group called Defend Job Philippines. They expressed outrage and slammed Duterte for not immediately coming to the aid of the Filipinos, and for allegedly selling "national sovereignty and integrity."

"Contrary to the strong-man persona that Duterte has been projecting against his critics, his weak positions against Chinese aggression and bullying only exposed himself as a pro-China and an anti-Filipino president," said Christian Lloyd Magsoy, a spokesman for the group.

"China is not just robbing our waters, land, resources and sovereignty, but has long been taking our jobs away from us," he said. "What makes it worse is that our own government seems to be allowing these crimes against us to happen."